Differential Diagnosis
- Single most likely diagnosis
- Osteochondroma or other benign bone tumor: The slow growth of the mass since 2015, its well-circumscribed nature, and the presence of internal gas (which could be due to necrosis or degenerative changes) suggest a benign process. The involvement of the pubic symphysis, an area prone to osteoarthritic changes, further supports this diagnosis.
- Other Likely diagnoses
- Ganglion cyst or synovial cyst: These are benign fluid-filled lesions that can occur near joints and could potentially contain gas due to degenerative changes. Their slow growth and well-circumscribed nature fit the described scenario.
- Bursitis: Chronic bursitis, especially in the context of osteoarthritis, could present as a soft tissue mass with potential gas content due to communication with the joint or degenerative changes.
- Do Not Miss
- Abscess or infected cyst: Although the scenario suggests a benign process and less likelihood of infection, it's crucial not to miss an abscess or infected cyst, as these conditions require urgent treatment. The presence of internal gas could also suggest an anaerobic infection.
- Malignant tumor (e.g., chondrosarcoma): While less likely given the slow growth and benign appearance, malignant tumors can sometimes present with similar characteristics. Missing a diagnosis of cancer could have significant consequences.
- Rare diagnoses
- Gouty tophus: In patients with chronic gout, tophi (deposits of monosodium urate crystals) can form in soft tissues and may mimic a mass. However, their typical appearance and the presence of internal gas make this a less likely diagnosis.
- Soft tissue chondroma: A rare benign tumor that could present similarly, but it's less common than other benign bone tumors or soft tissue lesions.